1. Field of the Invention
The present invention relates to an electromagnetic wave analysis apparatus, a design support apparatus, an electromagnetic wave analysis program, or a design support program that can evaluate the transmission and reception functions of electronic equipment such as a mobile telephone for transmitting and receiving electromagnetic waves.
2. Description of Related Art
In recent years, electronic equipment as typified by digital audiovisual equipment or a portable information terminal has become smaller and higher performance. As a result of reducing the size and improving the performance, the packaging density of a printed circuit board of the electronic equipment has increased. Moreover, the operating frequency of an integrated circuit (IC) mounted on the printed circuit board is very high. Thus, electromagnetic waves radiated from the printed circuit board, i.e., unwanted radiation noise may cause significant electromagnetic interference (EMI), including a transmission/reception disturbance and malfunction of the electronic equipment. An enormous amount of time and manpower is required to deal with the EMI.
As a conventional solution to the EMI problem, e.g., JP 2000-206163 A (Patent Document 1) has proposed an apparatus for measuring the intensity of an electromagnetic field in the vicinity of a circuit board of electronic equipment. This apparatus allows a loop antenna to get closer to the surrounding area of the circuit board. In such a case, an electric field and a magnetic field are present between the circuit board and the loop antenna, and currents generated by the electric field and the magnetic field are combined into a composite current that flows through the loop antenna. By measuring this composite current, it is possible to measure the electric field component and the magnetic field component of an electromagnetic field in the vicinity of the circuit board.
JP 8(1996)-221454 A (Patent Document 2) has proposed a simulation method for calculating the amount of crosstalk between the line patterns of a circuit board. In this simulation method, coupling coefficients that correspond to the combinations of coupled lines with various shapes and spaces of the line patterns are calculated and stored in a database. At the time of calculating crosstalk in any portion of a circuit to be analyzed, the coupling coefficient of a structure closest to the line patterns of the circuit is retrieved from the database.
JP 11(1999)-45294 A (Patent Document 3) has proposed a method for analyzing noise generated in the multiple lines of a circuit board. In this method, the multiple lines to be analyzed is divided into groups of two lines, and a noise waveform is calculated for each of the groups by simulation. Then, the noise waveforms of the groups of lines are synthesized to determine a noise waveform of the multiple lines.
JP 2000-19204 A (Patent Document 4) has proposed an apparatus that superimposes an intensity distribution map of noise caused by electromagnetic waves radiated from a board on image data for representation. In this apparatus, a micro-antenna probe for noise detection scans the board and measures noise due to the electromagnetic waves radiated from the board. The measured noise then is subjected to frequency analysis with a spectrum analyzer. The noise intensity distribution resulting from the analysis is superimposed on the image data of the board and displayed on a display.
Because of such a high-speed operating frequency of the IC mounted on the circuit board, the effect of unwanted radiation noise generated from the circuit board on the functions of transmitting and receiving electromagnetic waves of the electronic equipment cannot be ignored. However, the above conventional techniques merely propose the apparatus for measuring the electromagnetic waves generated from the electronic equipment. In other words, they do not propose an apparatus or method for obtaining information about how the unwanted radiation noise will affect the transmission and reception of electromagnetic waves by the electronic equipment. Therefore, it has been difficult to obtain information about the presence or absence of a transmission/reception disturbance due to the unwanted radiation noise or about a place where the transmission/reception disturbance occurs, e.g., in designing the electronic equipment such as a mobile telephone.